The present invention relates to a catalyst suitable for converting the carbonyl sulfide in gas into hydrogen sulfide in the presence of water vapor.
Since the sulfur compounds in various gases poison the catalysts used in various chemical processes or corrode the apparatuses used, vigorous efforts have been made in order to remove such sulfur compounds. Generally, it is necessary to remove sulfur compounds from effluent gases from the viewpoint of air pollution.
Of the sulfur compounds mixed in gases, H.sub.2 S and SO.sub.2 are relatively easy to remove, and can be removed by dry methods, in addition to wet methods such as alkali solution washing, amine absorption and the like. However, because carbonyl sulfide is difficult to remove by wet methods effectively, it is ordinarily converted into hydrogen sulfide by hydrolysis as below: EQU COS+H.sub.2 O.fwdarw.H.sub.2 S+CO.sub.2
The example of converting carbonyl sulfide in gas into hydrogen sulfide in the presence of water vapor can be observed when treating the tail gas of the Claus method. In this case, the catalysts used are usually titanium oxide, as the carrier, and oxides of transition metals such as iron, cobalt, nickel, molybdenum and the like as active ingredients. We have, however, found that the catalysts mentioned above suffer severe deterioration in the presence of hydrogen sulfide. In view of the fact that hydrolysis of carbonyl sulfide is unavoidably accompanied by the creation of hydrogen sulfide, the deterioration in activity may be a fatal defect to the catalysts for use in hydrolysis of carbonyl sulfide.